This invention relates generally to the control of a blasting operation.
A modern blasting system of the kind which is used for blasting operations in mines, quarries and the like typically makes use of electronic detonators, the number of which can vary and which are configured in a desired pattern, and a blast controller which can be used to program the detonators, if appropriate, and then arm and fire or initiate the detonators when necessary.
The blast controller is usually a complex device which is designed to exercise precise control over the blasting functions of the detonators and to eliminate or at least substantially reduce the likelihood of inadvertent firing of the detonators. It is known to make use of a blasting or activation key to enable the blast controller. This type of key can be physical in nature and generally is stored together with the blast controller at a blasting site. Clearly this represents a security risk in that if a person can gain access to the key the blast controller can be enabled without legitimate authorisation. A blasting system can thus be configured for unauthorised use, a possibility which holds significant adverse security implications.
U.S. Pat. No. 5,520,114 describes a technique in which a magnetic card is used to authorise a blast. U.S. Pat. No. 4,674,047 discloses a technique in which detonators are associated with a two-part security code, a first part being unique to a user and a second part being a firing control code. International patent application No. WO2004020934 describes a system of physical blasting keys to exercise control over the use of blast equipment. It is evident that these approaches concentrate primarily on local security control measures and fail to account for the fact that all the essential requirements for initiating a blast, namely the detonators, control equipment and access means such as keys or cards, are usually stored on the blasting site or in close proximity to each other and thus represent a security risk in the sense of unauthorised access and use.